Histological Analysis of Degenerate Discs (Disc Study)—is there Support for Infection as a Possible Etiology for Disc Degeneration?

Introduction A controversial study implicated bacterial factors in chronic back pain and reported a potential treatment option with long-term antibiotics. Currently, a multicentric case–control study is being conducted looking at bacterial in surgical disc specimens: Is growth a true infection or a contaminant? A histopathological arm has been added to aid in this differentiation. The aim of this study was to look for histopathological evidence of degeneration and inflammation and to identify histological differences in surgically excised disc samples of patients who grew bacteria on disc cultures compared with those that did not. Material and Methods A subset of patients as a part of a DISC study operated at Prince of Wales Public and Private Hospitals, Sydney were included in the study. The study was approved by HREC 13/218 started in 2013 and is ongoing. Cervical and lumbar disc samples were sent for both bacterial culture and histopathology. Histopathology was graded by two independent pathologists (blinded to culture results) using the previously evidenced histologic degeneration score (HDS) and a newly devised disc inflammatory score (DIS). Demographic factors, surgical factors and MODIC changes on MRI were correlated with histopathology data. Results There were 125 samples from 104 patients. Of the patients, there was a 54:50, male to female ratio. Discs levels from the cervical and lumbar regions were sampled (45:80, respectively). Of the total number of samples 33/125 (26.4%) grew bacteria, and 57.6% (19/33) of these grew Propionibacterium acnes. Using the HIS, only disc degeneration was found, with no significant evidence of inflammation in disc specimens. Conclusion In our histopathological study, there was no evidence of inflammation in degenerate discs and no differences in histopathology between positive and negative disc cultures. This raises a strong possibility of contamination in positive cultures of disc samples. In addition to this, there is further validation required of the new DIS score.